Technique for Performing Communication in a Wireless Communication Network

ABSTRACT

An aspect of the present disclosure is directed to a network node for performing communication in a wireless communication network. The network node is configured to receive a signal transmitted by a user device in the wireless communication network, measure a received power level at which the signal is received by the network node, determine, based on a predefined transmit power level of the network node, based on a predefined transmit power level of the user device and based on the received power level, a threshold power level for a clear channel assessment to be performed by the user device, and trigger transmitting an indication of the threshold power level to the user device. Further aspects of the disclosure pertain to a user device, methods and a computer program product.

TECHNICAL FIELD

The present disclosure generally relates to a technique for performingcommunication in a wireless communication network. In particular,methods and devices are disclosed for performing communication in awireless communication network, which can be, without limitation, awireless local area network, WLAN, operating in the IEEE 802.11 standardfamily. More specifically and without limitation, the disclosed devicesand methods may be implemented in the context of a clear channelassessment in a channel of the wireless communication network.

BACKGROUND

A commonly used approach for sharing a channel in unlicensed frequencybands (such as the 2.4 GHz frequency band used for wirelesscommunication according to the IEEE 802.11 WLAN standard family) isbased on carrier sense multiple access with collision avoidance(CSMA/CA). Effectively, a device that intends to make use of thewireless medium for transmission senses the channel and determineswhether the channel is busy (in the following also: “in use”, “used” or“occupied”) or idle (in the following also: “not in use”, “unused” or“unoccupied”). If the channel is determined to be busy, the transmissionis deferred whereas if the channel is determined to be idle atransmission is initiated. Just as the name “CSMA/CA” suggests, the ideais to avoid collisions by only initiating a transmission when thechannel is not already used by another transmitting device.

In the IEEE 802.11 standard family (which is directed to Wireless LocalArea Network, WLAN, communication), initiating a transmission usuallyrequires generating a random back-off value reducing the risk that twodevices that find the channel being idle start transmitting at the sametime. In practice, other transmission coordination mechanisms may beused too. The details regarding how this initiation of a transmission isimplemented are not part of the present disclosure since they are knownto the person skilled in the art from the specifications of therespective IEEE 802.11 standard. Therefore, these details are herein notdiscussed further.

A critical component of the CSMA/CA protocol is how to determine whetherthe channel is busy (“in use”, “used” or “occupied”) or idle (“not inuse”, “unused” or “unoccupied”). There are two fundamentally differentways to determine whether the desired channel is busy or idle. In thefirst approach, a receiver is searching for a specific (well-defined)signal or “preamble”. If found, the wireless medium (channel) isconsidered to be busy. Additionally, some implementations may considerthe channel to be busy only if the signal is above a specific thresholdvalue (a threshold power level). This approach is commonly referred toas signal detect or preamble detect (PD). IEEE 802.11 defines the PDthreshold for its OFDM (Orthogonal frequency-division multiplexing)radio designs to be set to −82 dBm or less in the unlicensed 2.4 GHz and5 GHz bands. That is, if a preamble of an IEEE 802.11 signal is detectedat a power level of −82 dBm or higher, the channel must be classified asbusy and a device must defer its transmission. On the contrary, if adevice detects a well-known signal at a power level below the PDthreshold level, the device may classify the channel as idle and mayinitiate a transmission. Often, however, an IEEE 802.11 STA (station, inthe following also: “user device”) applies a PD threshold level lowerthan the required −82 dBm. Specifically, the PD threshold oftencoincides with the sensitivity threshold for the STA, which may bearound −92 dBm. Basically, this means that the user device will defer toany successfully received transmission containing the well-known IEEE802.11 preamble.

However, sometimes, the channel, in which a transmitter (e.g., a userdevice) intents to transmit, may be occupied by a signal that, e.g., isgenerated by a dissimilar system (e.g., not a WLAN device). In thiscase, it is not sufficient to only use PD in order to determine whetherthe channel is busy or idle. Therefore, in addition to PD, an IEEE802.11 receiver sensing the channel also needs to consider the presenceof other signals. This is done by detecting the energy level of anysignal in the channel. In contrast to PD, this detection is performedindependently of the actual type of signal or known preambles. Thechannel is declared as busy if the energy level exceeds a predefinedthreshold level and the channel is considered to be unoccupied (idle)otherwise. This way of determining the state of the channel is commonlyreferred to as energy detect (ED). In IEEE 802.11, the threshold levelused for ED is −62 dBm.

As is readily understood, the lower the level that is used for declaringthe channel as idle, the less “aggressive” the user device is inaccessing the channel. So, comparing the levels for PD and ED, it can beconcluded that an IEEE 802.11 system is relatively “nice” to other IEEE802.11 systems in that it will not initiate a transmission if anotherIEEE 802.11 transmission at or exceeding −92 dBm (in practice) isdetected, whereas if the transmission is caused by another system, theIEEE 802.11 system will instead consider the ED threshold and defer fromtransmission if the observed energy level exceeds −62 dBm.

To see what this means in terms of range, one may consider somereasonable values for an IEEE 802.11 system. A reasonable transmission(TX) power is 15 dBm. Furthermore, if the system is operated at 2.4 GHza reasonable model for the propagation loss (PL) in dB is:

PL=40+35 log₁₀(d),   (1)

where the first term of 40 corresponds to the attenuation at a distanceof 1 m (d=1) and the distance d is given in meters. For another carrierfrequency than 2.4 GHz the constant will take another value.

With the typical PD and ED thresholds above, i.e., −92 dBm and −62 dBm,respectively, the corresponding PLs become 107 dB and 77 dB,respectively, for a transmit power of 15 dBm. Finally, using the aboveformula (1) for PL, it can be readily seen that this corresponds todistances of 82 m and 11 m, respectively.

At the same time, the required signal-to-noise-ration (SNR) for an IEEE802.11 system using the most robust modulation and coding scheme (MCS)may be around 2 dB, which corresponds to a PL of 107 dB and a range of82 m at 15 dBm transmit power. In fact, a PD threshold of −92 dBm isrepresentative of the sensitivity level for the lowest (most robust,slowest transmission speed) MCS today's radios are commonly capable of.The number is found as follows. The thermal receiver noise power at roomtemperature in a 1 MHz bandwidth is −114 dBm, which can be found inbooks on communication theory and using reasonable assumptions. With a20 MHz bandwidth, the noise power increases by 13 dB. Finally, we assumea radio implementation specific noise figure in the receiver of 7 dB,leading to a noise floor of −114 “dBm”+13 “dB”+7 “dB”=−94 “dBm”. With arequired SNR of 2 dB, the sensitivity level of −92 dBm is obtained.

FIG. 1 provides an illustration of the situation described above. Thestation STA1 1, which is assumed to be located in the center of thesmall circle 3, would only detect non-Wi-Fi transmissions using ED ifthe corresponding transmitters would be located within the small circle3. As calculated above, the small circle 3 is assumed to have a radiusof 11 m for the present exemplary consideration. Further, a “coveragearea” for an access point (AP) 5 has been calculated above to correspondto 82 m (assuming a sensitivity level of a receiver of −92 dBm). Thiscoverage area is indicated by the large circle 7.

Considering that the access point (AP) 5 is not located within the smallcircle 3 and that the area of the small circle 3 represents(11/82)̂2≈18/1000 of the coverage area of the AP 5 it becomes obviousthat using ED for detecting WLAN transmission is insufficient. Ifinstead PD is employed, the AP 5 operates within detection range, sinceit is located within the large circle 9 indicating a PD detection rangeof STA1 1.

Only STAs located in the opposite part of the AP's 5 coverage areacannot be detected under the described PD threshold.

The fact that the channel erroneously might be declared as idle when itin fact is busy is commonly referred to as the hidden node problem dueto the fact that the transmitter, which is not heard, is hidden from theSTA (STA1) performing the clear channel assessment (CCA). Hidden STAscenarios are susceptible to colliding transmissions. ARequest-To-Send/Clear-To-Send (RTS/CTS) message exchange is commonlyused counteracting this scenario. When a STA has data to send it sensesthe channel, and if found idle it transmits an RTS message to theintended receiver.

If the intended receiver successfully receives the RTS message itresponds with a CTS message indicating a period of time to devices inits surroundings that it requests other devices to defer from mediumaccess attempts.

However, cases may occur, in which a wireless communication system(e.g., a user device) is unable to perform preamble detection PD but canperform energy detection ED. In such a case, the choice of ED powerthreshold level, below which the wireless medium may be treated as idle,becomes the key parameter for determining performance. In known devices,in IEEE 802.11, the energy detection threshold is set to −62 dBm, asdiscussed above. As illustrated above, this value is too high foroperating with low collision probability. In case a new (additional)IEEE 802.11 operating mode would not be able to rely on PD but solelyoperate under energy detection rules, radio performance would bedetrimentally affected, which is a problem of prior art techniques.

In view of the above, known techniques and communication standards donot sufficiently deal with the aforementioned situation that a wirelessdevice only relies on ED for performing a clear channel assessment.

SUMMARY

Accordingly, there is a need for a technique which solves the aboveproblem or other related problems of prior art techniques. Specifically,and without limitation, there is a need for a technique that may beapplied in case a wireless device (e.g., a user device) only relies onenergy detect (ED) to perform clear channel assessment (CCA).

According to a first aspect, a network node for performing communicationin a wireless communication network is provided. The network node isconfigured to receive a signal transmitted by a user device in thewireless communication network, measure a received power level at whichthe signal is received by the network node, determine, based on apredefined transmit power level of the network node, based on apredefined transmit power level of the user device and based on thereceived power level, a threshold power level for a clear channelassessment to be performed by the user device, and trigger transmittingan indication of the threshold power level to the user device.

According to a second aspect, a network node for performingcommunication in a wireless communication network is provided. Thenetwork node comprises a network interface that is adapted tocommunicatively couple the network node to the wireless communicationnetwork, a processor, and a memory. The memory contains instructionsexecutable by the processor to cause the network node to receive asignal transmitted by a user device in the wireless communicationnetwork, measure a received power level at which the signal is receivedby the network node, determine, based on a predefined transmit powerlevel of the network node, based on a predefined transmit power level ofthe user device and based on the received power level, a threshold powerlevel for a clear channel assessment to be performed by the user device,and trigger transmitting an indication of the threshold power level tothe user device.

According to a third aspect, a network node for performing communicationin a wireless communication network is provided. The network nodecomprises a receiving unit configured to receive a signal transmitted bya user device in the wireless communication network, a measuring unitconfigured to measure a received power level at which the signal isreceived by the network node, a determining unit configured todetermine, based on a predefined transmit power level of the networknode, based on a predefined transmit power level of the user device andbased on the received power level, a threshold power level for a clearchannel assessment to be performed by the user device, and a triggeringunit configured to trigger transmitting an indication of the thresholdpower level to the user device.

The following description may apply to all aspects described in thisdisclosure. In particular, the following description concerning theapparatus aspects may not only apply to the apparatus aspects but alsoto the method aspects described below, where applicable.

Although the following description will be given with reference to awireless local area network (WLAN), the present application is notlimited to a WLAN and the described wireless communication network maybe any suitable kind of wireless communication network, including a WLANaccording to the standard family IEEE 802.11 (e.g., IEEE 802.11a, g, n,ax or ac; also referred to as Wi-Fi), a Worldwide Interoperability forMicrowave Access (WiMAX) according to the standard family IEEE 802.16and/or a wireless network operating under a 3rd Generation PartnershipProject (3GPP) standard, such as LTE or any other mobile communicationstandard.

The network node may be any wireless device in the wirelesscommunication network. In particular, the network node may be an AccessPoint (AP) of a WLAN network or a base station, Node B or eNodeBoperating under a 3GPP standard. Accordingly, the wireless communicationnetwork may be any suitable communication network, including a WLAN or amobile communication network operating under a 3GPP standard, such as anLTE network. Further, the user device may be any wireless device in thewireless communication network, which is adapted to perform a clearchannel assessment in a channel of the wireless communication network.In particular, the user device may be a station (STA) of a WLAN or aUser Equipment (UE) of a 3GPP wireless communication network.

The received power level may indicate a measured power level, e.g., inmW, dBm or any other suitable unit. Besides measuring the received powerlevel, the received signal is not necessarily further processed by thenetwork node. The predefined transmit power level of the user device maybe a power level (e.g., a standard power level), which is known to thenetwork node. In other words, the predefined transmit power level of theuser device may be stored in a memory of the network node and may beretrieved from this memory for determining the threshold power level.The predefined transmit power level of the user device does notnecessarily need to correspond to a power level at which the user deviceis actually transmitting but it may also correspond to a standard value,a mean value, an initial value or any other kind of suitable value. Thepredefined power level may have been written into a memory of thenetwork node in a configuration step or the value of the predefinedpower level may have been transmitted to the network node, e.g., fromthe user device. For example, the predefined transmit power level of theuser device may be 15 dBm.

Determining based on one or more parameters may mean, according to theentire present disclosure, that a value is determined as result of apredefined calculation, wherein the one or more parameters are used(i.e., have an influence) in the calculation, e.g., as variables of anequation.

The predefined transmit power level of the network node may be a powerlevel at which the network node is currently transmitting at the time ofdetermining the threshold power level. Additionally or alternatively,the predefined transmit power level of the network node may be a valuestored in a memory of the network node. In some embodiments, thepredefined transmit power level of the network node may correspond to astandard value or a mean value. For example, the predefined transmitpower level of the network node may be 15 dBm.

The threshold power level may be determined based on the followingequation:

P_threshold=P_transmit_NN/(P_transmit_UD/P_received),   (3)

where P_threshold is the threshold power level, P_transmit_NN is thepredefined transmit power level of the network node, P_transmit_UD isthe predefined transmit power level of the user device and P_received isthe received power level. In case the power level P_transmit_NN is givenin dBm and the power levels P_transmit_UD and P_received are given indBm, the threshold power level P_threshold in dBm can be calculated asP_threshold (in dBm)=P_transmit_NN (in dBm)−P_transmit_UD (indBm)+P_received (in dBm). In this disclosure, the threshold power levelP_threshold is also referred to as ED_DL, to reflect that it related tothe energy that would be detected for a downlink transmission, i.e., atransmission from the AP to the STA.

According to the entire present disclosure, the expression “trigger” maymean that the step following this expression is performed by the devicethat is configured to trigger the step or by another device, which is incommunication with the device configured to trigger the step. Forexample, the device configured to trigger the step may transmit atrigger message to another device, which performs the step, wherein thetrigger message may include further parameters necessary for performingthe step.

The indication of the threshold power level may include, e.g., a valueof the threshold power level or other data, based on which the thresholdpower level can be adjusted or set at the user device. For example, theindication of the threshold power level may comprise a number (e.g., 1,2, 3, etc.), based on which the user device may select a correspondingthreshold power level from a look-up table (that may be stored in amemory of the user device).

The network node may further be configured to determine, based on thereceived power level and based on the predefined transmit power level ofthe user device, a path loss of the signal transmitted from the userdevice to the network node. In that case, the network node may beconfigured to determine the threshold power level based on thepredefined transmit power level of the network node and based on thepath loss.

The path loss may be determined so as to correspond to the ratio of thepredefined transmit power level of the user device and the receivedpower level. In other words, the path loss (PL) may be determined basedon the following equation:

PL=P_transmit_UD/P_received,   (4)

where PL is the path loss, P_transmit_UD is the predefined transmitpower level of the user device and P_received is the received powerlevel. In case the power levels

P_transmit_UD and P_received are given in dBm, the path loss in dB canbe calculated as PL (in dB)=P_transmit_UD (in dBm)−P_received (in dBm).

The threshold power level may be determined so as to correspond to theratio of the predefined transmit power level of the network node and thepath loss. In other words, the threshold power level may be determinedbased on the following equation:

P_threshold=P_transmit_NN/PL,   (5)

where P_threshold is the threshold power level, P_transmit_NN is thepredefined transmit power level of the network node and PL is the pathloss. In case the power level P_transmit_NN is given in dBm and the pathloss PL is given in dB, the threshold power level P_threshold in dBm canbe calculated as P_threshold (in dBm)=P_transmit_NN (in dBm)−PL (in dB).In this disclosure, the threshold power level P_threshold is alsoreferred to as ED_DL, to reflect that it related to the energy thatwould be detected for a downlink transmission, i.e., a transmission fromthe AP to the STA.

The network node may further be configured to set a desired maximumreceived power level for signals to be received by the network node fromthe user device, determine, based on the maximum received power leveland based on the path loss, a maximum transmit power level for signalstransmitted by the user device, and trigger transmitting an indicationof the maximum transmit power level to the user device.

The desired maximum received power level may be set to a predefinedvalue. The predefined value may be stored, e.g., in a memory of thenetwork node. For example, the desired maximum received power level maycorrespond to −97 dBm. The desired maximum power level may be set to avalue, which does not have a significant impact on the reception ofsignals received by the network node from another user device.

In view of the above, setting the desired maximum received power levelmay include one or more calculation steps but it may also relate to astep of considering a predefined, known, power level.

The maximum transmit power level may be determined so as to correspondto the product of the maximum received power level and the path loss. Inother words, the maximum transmit power level may be determined based onthe following equation:

P_transmit_max_UD=P_received_max_NN*PL,   (6)

where P_transmit_max_UD is the maximum transmit power level for signalstransmitted by the user device, P_received_max_NN is the desired maximumreceived power level for signals to be received by the network node fromthe user device and PL is the path loss. In case the power levelP_received_max_NN is given in dBm and the path loss PL is given in dB,the maximum transmit power level P_transmit_max_UD in dBm can becalculated as P_transmit_max_UD (in dBm)=P_received_max_NN (in dBm)+PL(in dB). In this disclosure, the maximum transmit power level is alsoreferred to as TX_UL.

The indication of the maximum transmit power level may include, e.g., avalue of the maximum transmit power level or other data, based on whichthe maximum transmit power level can be adjusted or set at the userdevice. For example, the indication of the maximum transmit power levelmay comprise a number (e.g., 1, 2, 3, etc.), based on which the userdevice may select a corresponding maximum transmit power level from alook-up table.

The network node may be configured to set the desired maximum receivedpower level for signals to be received by the network node from the userdevice so as to correspond to a predefined proportion of a thermal noisepower level of signals received by the network node.

The thermal noise power level may be a value known to the network node.For example, the thermal noise power level may be a value stored in amemory of the network node. The thermal noise power level may be athermal noise power level at a bandwidth of 20 MHz. The thermal noisepower level may be −94 dBm. The predefined proportion may be given as avalue in dB. In other words, the maximum received power level may bedetermined so as to correspond to the ratio of the thermal noise powerlevel and a predefined value. Since the predefined value may be given indB, it may also be regarded as an offset value (P_offset). This offsetvalue may be 3 dB. In other words, the maximum received power level maybe determined based on the following equation:

P_received_max_NN=P_noise/P_offset,   (7)

where P_received_max_NN is the desired maximum received power level forsignals to be received by the network node from the user device, P_noiseis the thermal noise power level and P_offset defines the predefinedproportion. In case the noise power level P_noise is given in dBm andthe predefined proportion P_offset is given in dB, the maximum receivedpower level P_received_max_NN in dBm can be calculated asP_received_max_NN (in dBm)=P_noise (in dBm)−P_offset (in dB).

The network node may further be configured to receive data transmittedfrom the user device. For example, the network node may be configured toreceive the data in a narrow bandwidth channel, such as a channel havinga bandwidth of 2 MHz. The communication from the user device to thenetwork node may be referred to as uplink, uplink communication, uplinkchannel, etc. Communication from the network node to the user device maybe referred to as downlink, downlink communication, downlink channel,etc. The data may be received from the network node after the thresholdpower level has been transmitted to the user device. Further, the datamay be transmitted by the user device, after the user device hassuccessfully performed a clear channel assessment in the channel inwhich the data is transmitted.

The network node may further be configured to transmit signals using anorthogonal frequency-division multiple access, OFDMA, modulation schemein which one or more resource units, RUs, are assigned for transmissionsto and/or from a particular user device. In this case, the network nodemay further be configured to receive a signal transmitted by the userdevice, determine, based on the received signal, one or more RUs of theOFDMA modulation scheme used by the network node, in which the receivedsignal is transmitted by the user device, exclude the one or more RUsfrom a list of RUs available for transmissions from the network node toa further user device, and trigger transmitting data to the further userdevice by using one or more RUs of the list of RUs.

The OFDMA modulation scheme may, e.g., be an OFDMA modulation scheme ofthe IEEE 802.11ax standard. The signals transmitted using the OFDMAmodulation scheme may be transmitted using one or more resource units(RUs) distributed within a bandwidth of 20 MHz. In that case, an OFDMAmodulation scheme for a 20 MHz bandwidth of the IEEE 802.11ax standardmay be used.

The signal received from the user device may be a signal transmitted ina narrow band channel, e.g., in a channel having a bandwidth of 2 MHz.Generally speaking, the signal received from the user device may betransmitted in a channel having a bandwidth smaller than the bandwidthused for the OFDMA transmission performed by the network node. Abandwidth of a channel in which the signal is transmitted by the userdevice may be equal to or smaller than one RU of the OFDMA modulationscheme.

The expression “further user device” according to the present disclosureis merely used to distinguish the “further user device” from the “userdevice” and has no additional technical meaning. Therefore,alternatively, also the expression “first user device” may be used forthe “user device” and the expression “second user device” may be usedfor the “further user device”. Similar considerations hold for theexpression “further STA”, which could synonymously also be referred toas “second STA”.

The step of determining one or more RUs of the OFDMA modulation schemeused by the network node may comprise determining one or more RUs, afrequency bandwidth of which at least partially overlaps a frequencybandwidth of the received signal from the user device. For example, ifthe bandwidth of the received signal is smaller than one RU, it might bethe case that the signal entirely lies within the bandwidth of one RUand in this case, this RU is determined. However, in case the receivedsignal overlaps two or more RUs, these two or more RUs may bedetermined.

Excluding the one or more RUs may mean that these RUs are not consideredin a following selection process for one or more RUs in which datatransmission to a further user device is performed using the OFDMAmodulation scheme. In other words, the network node will not use thedetermined one or more RUs for a following data transmission to thefurther user device.

As stated above, the network node may be configured to transmit signalsusing an orthogonal frequency-division multiple access, OFDMA,modulation scheme in which one or more resource units, RUs, are assignedfor transmissions to and/or from a particular user device. In this case,the network node may further be configured to receive a signaltransmitted by the user device, determine, based on the received signal,one or more RUs of the OFDMA modulation scheme used by the network node,in which the received signal is transmitted by the user device, excludethe one or more RUs from a list of RUs available for transmissions froma further user device to the network node, and trigger scheduling atransmission from the further user device to the network node by usingone or more RUs of the list of RUs.

Regarding the OFDMA modulation scheme and regarding the steps ofreceiving and determining, the same aspects as discussed above may alsobe valid in this case. Further, regarding the step of excluding, similarconsiderations with regard to the aforementioned step of excluding mayapply.

Excluding the one or more RUs may mean that these RUs are not consideredin a following selection process for one or more RUs in which datatransmission from a further user device to the network node isscheduled, wherein the scheduled data transmission is performed usingthe OFDMA modulation scheme. The scheduling is triggered (and/orperformed) by the network node. In other words, the network node willnot use the determined one or more RUs for a following scheduling ofdata transmission from the further user device to the network node.

The network node may be configured such that the step of triggeringscheduling the transmission from the further user device to the networknode comprises transmitting a scheduling message to the further userdevice, wherein the scheduling message comprises an indication of theone or more RUs of the list of RUs to be used by the further user devicefor the transmission from the further user device to the network node.

In that way, the network node can assign one or more RUs to an uplinkcommunication of data transmitted from the further user device to thenetwork node. The network node can thereby maintain an overview of theindividual communications (in particular, the OFDMA communications)performed in the wireless network. For example, the network node canassign other RUs to an uplink communication of data transmission from a2nd further user device to the network node. These other RUs may alsonot include the previously mentioned excluded one or more RUs.

The wireless communication network may be a wireless local area network,WLAN, operating in the IEEE 802.11 standard family and the network nodemay comprise an access point of the WLAN. The access point may be anaccess point (AP) of the WLAN according to the used IEEE 802.11standard.

The wireless communication network may be a wireless local area network,WLAN, operating in the IEEE 802.11 standard family and the user devicemay comprise a station, STA, of the WLAN. The station may be a station(STA) of the WLAN according to the used IEEE 802.11 standard.

The network node may be configured to communicate with a first type ofuser device and a second type of user device, wherein the second type ofuser device supports wider bandwidths than the first type of userdevice.

In other words, the network node may be configured to communicate withthe first type of user device using a first bandwidth and with a secondtype of user device using a second bandwidth, wherein the firstbandwidth is narrower than the second bandwidth. Within this disclosure,the first bandwidth will also be referred to as a narrow bandwidth (NB)and the second bandwidth will also be referred to as a wide bandwidth.For example, the narrow bandwidth may refer to a bandwidth of 2 MHz.Further, the wide bandwidth may refer to a bandwidth of 20 MHz.

The first type of user device may, for example, only supportcommunication within a bandwidth of 2 MHz or less.

The second type of user device may support, for example, communicationwithin a bandwidth of 10 MHz or more (e.g., 20 MHz).

According to a fourth aspect, a user device for performing communicationin a wireless communication network is provided. The user device isconfigured to receive, from a network node of the wireless communicationnetwork, a threshold power level for a clear channel assessment to beperformed by the user device in the wireless communication network,receive, from the network node, a maximum transmit power level forsignals transmitted by the user device, trigger performing the clearchannel assessment in a channel of the wireless communication network,and, in case the channel is determined to be idle, transmit data to thenetwork node in the wireless communication network at a transmit powerlevel equal to or lower than the maximum transmit power level.

According to a fifth aspect, a user device for performing communicationin a wireless communication network is provided. The user devicecomprises a network interface that is adapted to communicatively couplethe user device to the wireless communication network, a processor, anda memory. The memory contains instructions executable by the processorto cause the user device to receive, from a network node of the wirelesscommunication network, a threshold power level for a clear channelassessment to be performed by the user device in the wirelesscommunication network, receive, from the network node, a maximumtransmit power level for signals transmitted by the user device, triggerperforming the clear channel assessment in a channel of the wirelesscommunication network, and, in case the channel is determined to beidle, transmit data to the network node in the wireless communicationnetwork at a transmit power level equal to or lower than the maximumtransmit power level.

According to a sixth aspect, a user device for performing communicationin a wireless communication network is provided. The user devicecomprises a first receiving unit configured to receive, from a networknode of the wireless communication network, a threshold power level fora clear channel assessment to be performed by the user device in thewireless communication network, a second receiving unit configured toreceive, from the network node, a maximum transmit power level forsignals transmitted by the user device, a triggering unit configured totrigger performing the clear channel assessment in a channel of thewireless communication network, and a transmitting unit configured to,in case the channel is determined to be idle, transmit data to thenetwork node in the wireless communication network at a transmit powerlevel equal to or lower than the maximum transmit power level.

The user device of any of the fourth to sixth aspect may correspond tothe user device from which the network node of any of the first to thirdaspect receives a signal. The details described above with regard todetails of the network node of the first to third aspect may applyaccordingly to the user device of the fourth to sixth aspect.

According to a seventh aspect, a method for performing communication ina wireless communication network is provided. The method is performed bya network node and the method comprises receiving a signal transmittedby a user device in the wireless communication network, measuring areceived power level at which the signal is received by the networknode, determining, based on a predefined transmit power level of thenetwork node, based on a predefined transmit power level of the userdevice and based on the received power level, a threshold power levelfor a clear channel assessment to be performed by the user device, andtriggering transmitting an indication of the threshold power level tothe user device.

The method of the seventh aspect may be performed by a device of any ofthe first to third aspect.

The details of the network node of the first to third aspect may alsoapply to the method of the seventh aspect in a sense that the networknode is configured to perform the method of the seventh aspect. In otherwords, the method of the seventh aspect may comprise steps correspondingto the aforementioned device features of the first to third aspect.

According to an eighth aspect, a method for performing communication ina wireless communication network is provided. The method is performed bya user device and the method comprises receiving, from a network node ofthe wireless communication network, a threshold power level for a clearchannel assessment to be performed by the user device in the wirelesscommunication network, receiving, from the network node, a maximumtransmit power level for signals transmitted by the user device,triggering performing the clear channel assessment in a channel of thewireless communication network, and, in case the channel is determinedto be idle, transmitting data to the network node in the wirelesscommunication network at a transmit power level equal to or lower thanthe maximum transmit power level.

The method of the eighth aspect may be performed by a device of any ofthe fourth to sixth aspect.

The details of the user device of the fourth to sixth aspect may alsoapply to the method of the eighth aspect in a sense that the user deviceis configured to perform the method of the eighth aspect. In otherwords, the method of the eighth aspect may comprise steps correspondingto the aforementioned device features of the fourth to sixth aspect,and, if applicable, of the first to third aspect.

According to a ninth aspect, a computer program product is provided. Thecomputer program product comprises program code portions to perform thesteps of any of the methods described in this disclosure when thecomputer program product is executed on one or more processing devices.The processing device may be or may comprise, e.g., a network node or auser device according to the present disclosure.

The computer program product of the ninth aspect may be stored on one ormore computer-readable recording media, such as, e.g., optical recordingmedia, magnetic recording media, solid state recording media, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details of embodiments of the technique are described withreference to the enclosed drawings, wherein:

FIG. 1 shows an illustration of energy detect (ED) and preamble detect(PD) performed by a station (STA1) in a WLAN;

FIG. 2 shows an example of an arrangement based on which the techniqueof the present disclosure is illustrated;

FIG. 3 shows a further example of an arrangement based on which thetechnique of the present disclosure is illustrated;

FIG. 4 shows resource units (RUs) used for a 20 MHz channel in IEEE802.11ax;

FIG. 5 shows a flowchart of a method for performing communication in awireless communication network performed by a network node, according tothe present disclosure;

FIG. 6 shows a schematic representation of a network node for performingcommunication in a wireless communication network, according to thepresent disclosure;

FIG. 7 shows a flowchart of a method for performing communication in awireless communication network performed by a user device, according tothe present disclosure;

FIG. 8 shows a schematic representation of a user device for performingcommunication in a wireless communication network, according to thepresent disclosure; and

FIG. 9 shows a schematic representation of a device for performingcommunication in a wireless communication network, according to thepresent disclosure, wherein the device may be a network node or a userdevice.

DETAILED DESCRIPTION

In the following description, for purposes of explanation and notlimitation, specific details are set forth, such as a specific networkenvironment in order to provide a thorough understanding of thetechnique disclosed herein. It will be apparent to one skilled in theart that the technique may be practiced in other embodiments that departfrom these specific details. Moreover, while the following embodimentsare primarily described for Wireless Local Area Network (WLAN) and theIEEE 802.11 standard family (e.g., IEEE 802.11a, g, n, ax or ac; alsoreferred to as WLAN or Wi-Fi), it is readily apparent that the techniquedescribed herein may also be implemented in many other wirelesscommunication networks, which are based on Carrier Sense MultipleAccess/Collision Avoidance (CSMA/CD). Such communication networks mayinclude a 3G, 4G or 5G wireless communication network operating under a3GPP standard, such as Long Term Evolution (LTE) and/or a WorldwideInteroperability for Microwave Access (WiMAX) according to the standardfamily IEEE 802.16.

Moreover, those skilled in the art will appreciate that the services,functions, steps and units explained herein may be implemented usingsoftware functioning in conjunction with a programmed microprocessor, anApplication Specific Integrated Circuit (ASIC), a Field ProgrammableGate Array (FPGA), a Digital Signal Processor (DSP) or a general purposecomputer, e.g., including an Advanced RISC Machine (ARM). It will alsobe appreciated that, while the following embodiments are primarilydescribed in context with methods and devices, the embodiments may alsobe embodied in a computer program product as well as in a systemcomprising a computer processor and memory coupled to the processor,wherein the memory is encoded with one or more programs that may performthe services, functions, steps and implement the units disclosed herein.

Further, in the following, specific devices (in particular a networknode and a user device) are described, which perform or are configuredto perform certain steps of a method. However, it will be appreciated bythose skilled in the art, that those steps do not necessarily have to beperformed by one single device but may be performed by different devicesthat are communicatively coupled with each other. For example, more thanone device may be provided and/or more than one processor may beprovided, wherein the steps are distributed among the devices and/orprocessors. Further, a cloud computing environment may be used forperforming the steps of one or more of the methods described herein.

According to the present disclosure and without limitation, it isproposed to adapt an energy detect (ED) threshold used by a station(STA) based on the channel conditions. Furthermore, it is proposed thata suitable threshold level may be determined by the access point (AP)and communicated to the associated STA. The threshold may be determinedbased on downlink (DL) conditions, and may be selected such that theprobability of channel use is maximized under the constraint that thethreshold will prevent or limit collisions with ongoing transmissions.In addition, the AP may determine the maximum transmit power to be used.In this way transmissions form STAs can be avoided using ED only todegrade performance of the legacy system.

Generally speaking and without limitation, the present disclosure may beimplemented in a WLAN environment, in which one access point (AP) is inwireless communication with a plurality of stations (STAs). At least oneof the STAs may be a legacy STA (or wideband STA) which is configured tocommunicate with the AP in a wideband channel having a wide bandwidthof, e.g., 20 MHz. Further, at least one of the STAs may be a STA(narrowband STA, NB-STA, or NB-Wi-Fi STA) which is configured tocommunicate with the AP in a narrowband channel having a narrowbandwidth of, e.g., 2 MHz. In that constellation, it may be the casethat the NB-STA is only configured to operate in the narrowband channeland is not able to detect preambles transmitted by the wideband STA.Therefore, the NB-STA may not be able to perform PD and has to rely onED for using a clear channel assessment in case the NB-STA intents totransmit data to the AP (e.g., when no data transmission has beenscheduled by the AP).

To ease the description of the present disclosure, specific systemparameters are used. However, as should be obvious for anyone ofordinary skill in the art, the disclosure is not limited to thesechoices of parameters. Also, the terminology used is that commonly usedin IEEE 802.11. E.g., the term access point (AP) is used when referringto the network node. However, equivalent terms for instance are basestation, node B (NB), or evolved node B (eNB). Similarly, the termStation (STA) is used when referring to a non-network node. Equivalentterms are user equipment (UE), user device, device, etc.

Suppose that an AP supports two different types of STAs, one able totransmit and receive high data rates at a wide bandwidth (a widebandSTA), the other limited to transmit and receive at lower data ratesusing a narrow bandwidth (a narrowband STA). To be more specific, anexample of the former STA (wideband STA) would be one compliant with802.11 a, b, g, n, ac, or ax, able to transmit and receive signals of 20MHz or potentially more, e.g. 40 MHz, 80 MHz, or even 160 MHz.

All wideband packets sent by STAs compliant with any of theaforementioned standards contain a preamble. Specifically, thispreamble, henceforth referred to as a legacy preamble, is used by allversions as means to ensure backward compatible signal (transmission)detection. Hence legacy equipment may perform PD for packets whoseactual data may be transmitted in a format not decodable by the samelegacy device.

This backward compatibility approach comes at the cost of additionaloverhead. However, it is a simple and robust mechanism. Inherently thisapproach requires future generations of the standard also to support theolder versions of the standard. In the past, when evolving standards hasbeen in the direction of increasing the supported data rate, thisbecomes natural and essentially comes at no additional cost since theold version of the standard often can be seen as a subset of the newerversion. However, when a newer version of a standard instead targetslower power consumption and lower cost, also supporting legacy operationcould completely ruin the possibility to achieve these goals. As a veryobvious example, if the legacy signal is 20 MHz wide, and the newversion of the standard targets to achieve low power consumption and lowcost by reducing the bandwidth a factor of 10, to 2 MHz, also supporting20 MHz reception does not make sense.

Thus, as the legacy preamble is sent over 20 MHz, it cannot be decodedby a STA (NB-STA) only supporting 2 MHz bandwidth. Thus, the only optionthat remains for a NB-Wi-Fi STA is to rely on ED in case it has todetermine whether the channel is idle or busy. As discussed above,performing ED with the default parameters will almost never work as theprobability that another STA is sufficiently close for the channel to bedeclared as busy is very small, and thus the channel will likely beerroneously declared as idle and potentially cause a collision. In thepresent disclosure this problem is addressed.

A goal is that a NB-STA should be able to perform ED, and based on thisdetermine whether it is allowed to transmit or not. And if it is allowedto transmit, this may also be under a constraint of a limitedtransmission power.

To ensure that no harm to an ongoing transmission is done, potential DLand UL transmissions (between AP and a further STA, e.g., a widebandSTA) are considered separately.

DL (downlink; transmission from AP to a further STA): If thetransmission is in the

DL, i.e., from the AP to the further STA, the AP can accurate estimateat what level a NB-STA will receive the signal. This power level isdenoted as ED_DL, to reflect that this is the threshold level that wouldbe appropriate to use for the NB-STA in order to determine whether a DLtransmission is ongoing. ED_DL is also referred to as P_thresholdherein.

UL (uplink; transmission from a further STA to AP): If the transmissionis in the UL, i.e., from the further STA to the AP, the power receivedat the NB-STA will depend on which one of the STAs is transmitting inthe UL. This can vary considerably, and in particular it could be sothat the STA simply cannot be heard at all. To allow the NB-STA toaccess the channel, still ensuring that no harm is made, the AP uses adifferent approach. In case of an UL transmission, on the other hand,the AP knows roughly what the received power will be from the differentSTAs potentially transmitting in the UL. As the AP also approximatelyknows the path-loss between the NB-Wi-Fi STA and the AP, it candetermine at what power the NB-STA can transmit without significantlydegrading an UL transmission from another STA. This maximum allowed TXpower is denoted as TX_UL, to reflect that this is a limit related tothe transmit power for the UL. TX_UL is also referred to asP_transmit_max_UD.

So, by use of the ED_DL it is ensured that a DL transmission is notruined as it is ensured that a NB-Wi-Fi STA will not initiate atransmission. However, for the UL, the way it is ensured that no harm iscaused, is by potentially limiting the TX power of the NB-STA.

Thus, for the UL no attempt is made to avoid collisions, instead what isguaranteed is that if a NB-Wi-Fi transmission is made at the same timeas a wideband system, the NB-Wi-Fi signal is sufficiently weak so thatthe wideband system will still work. The NB-Wi-Fi signal may not becorrectly received, but this just has the effect that the NB-Wi-Fi STAhas to make a new attempt, just as it is usually done in a contentionbased system when a packet is not acknowledged.

According to some embodiments, the AP determines an ED_DL value, a TX_ULvalue and communicates these two values to a NB-Wi-Fi STA. The NB-Wi-FiSTA then uses these values to determine if it can access the channel,and if it can access the channel what transmission power can be used.Note that both ED_DL and TX_UL may be largely different for differentNB-Wi-Fi STAs depending on their relative location to the AP. In someembodiments, however, only the ED_DL is determined and communicated to aNB-STA and no TX_UL value is determined and communicated.

To give a numerical example of the embodiments described above,according to which an ED_DL value and a TX_UL value are determined andtransmitted, FIG. 2 is considered. FIG. 2 shows an example of a simpledeployment with one legacy STA (STA1) 11 and one NB-Wi-Fi STA (NB-STA)13 connected to the AP 15.

As shown in FIG. 2, according to the example, a path loss between AP 15and STA1 11 is 80 dB, a path loss between AP 15 and NB-STA 13 is 100 dBand a path loss between STA1 11 and NB-STA 13 is 120 dB.

In the following, to illustrate the problem of the prior art, it will bebriefly described what would happen in case prior art ED was applied tothe arrangement of FIG. 2. If ED would be employed according to priorart, using the same levels as are currently used in IEEE 802.11, the EDlevel measured in a 2 MHz bandwidth would be −72 dBm (10 dB lower thanthe −62 dBm measured in a 20 MHz channel). Clearly, if the NB-Wi-Fi STA13 would use this ED threshold, the channel would always be found beingidle as the receiver power in 2 MHz in case of DL transmission would be−95 dBm and in case of UL transmission would be −115 dBm. It is hereassumed that the transmission power used by both the AP 15 and STA1 11is 15 dB.

Considering what will happen if the NB-Wi-Fi STA 13 initiates atransmission when a DL communication is ongoing, it is readily seen thatthe AP 15 will not be able to receive it as it is currentlytransmitting. Considering an UL transmission, the received power at theAP 15 will be −85 dBm within a 2 MHz channel. At the same time thereceived power from STA1 11 will be −65 dBm. However, the thermal noisein the AP 15 in a 20 MHz channel will be in the order of −114 dBm/MHz+13dBMHz+7 dB =−94 dBm, where −114 dBm/MHz is the thermal noise powerwithin a 1 MHz channel, 13 dBMHz comes from the consideration that a 20MHz channel will have 13 dB more noise than a 1 MHz channel, and 7 dB isassumed to be the noise figure of the receiver.

Thus, without interference from the NB-Wi-Fi transmission thesignal-to-noise-ratio (SNR) is −65 −(−94)=29 dB. However, NB-Wi-Fiinterference present, the signal-to-interference-ratio (SIR) becomes −64−(−85)=21 dB. Thus, if noise and interference is treated as having thesame effect on the desired signal, the signal quality of the signalreceived from STA1 11 is degraded by 8 dB. Assuming that the modulationand coding (MCS) used for transmission from STA1 11 to the AP 15 isadapted to the channel conditions of 29 dB SNR, reception would almostcertainly fail if the signal quality drops to around 21 dB, clearlyillustrating the problem with using ED for determining whether thechannel is idle or busy.

Now, according to the present embodiment the AP 15 estimates ED_DL.Since the AP 15 knows the TX power used by the NB-Wi-Fi STA 13 andcorresponding power is this easily done. In this particular example thetransmitted power was 15 dBm, the received power −85 dBm, andconsequently path loss is 100 dB. In this particular case the transmitpowers were the same for the AP 15 and the NB-Wi-Fi 13, which results inthat ED_DL becomes the same as the received power at the AP 15, i.e.,−85 dBm. Thus, the NB-Wi-Fi STA 13 should perform ED with ED_DL=−85 dBm.

Next, it is considered what is required in order to not significantlydegrade the performance for an UL transmission from STA1 11 to the AP15. According to the calculations above, the thermal noise power is −94dBm in a 20 MHz bandwidth. Suppose it is required that the power of theNB-Wi-Fi transmission when received at the AP 15 should be at least 3 dBlower in order to not have a significant impact, i.e., the maximum powerreceived from the NB-Wi-Fi STA 13 should not exceed −97 dBm.

Since the path loss is 100 dB, it follows that the maximum output powerthat is allowed for the NB-Wi-Fi STA 13 is 3 dBm. So the AP 15 sendsthis information to the NB-Wi-Fi STA 13, i.e., that in order to accessthe channel it must use ED with a threshold of −85 dBm. In case thechannel is found to be idle, the NB-Wi-Fi STA 13 may transmit but notusing a TX power exceeding 3 dBm.

Reducing the power of the NB-Wi-Fi signal in order not to causeinterference to an ongoing UL transmission can of course only be done toa certain point if the AP 15 should still be able to receive theNB-Wi-Fi signal. What is worth noting is the SNR of the NB-Wi-Fi signalat the AP 15 will benefit from that the bandwidth is much smaller. So,although the received power of the NB-Wi-Fi signal should not exceed −97dBm, the SNR within a 2 MHz channel becomes 7 dB since the noise powerwithin a 2 MHz channel becomes −104 dBm still assuming a 7 dB noisefigure. A SNR of 7 dB would typically allow for successful reception ofa NB-Wi-Fi signal at the AP 15.

To provide another example, FIG. 3 is considered, which is similar toFIG. 2 but with STA1 11 and the NB-Wi-Fi STA 13 swapped with regard totheir position. In other words, according to the example discussed withregard to FIG. 3, a path loss between AP 15 and STA1 11 is 100 dB, apath loss between AP 15 and NB-STA 13 is 80 dB and a path loss betweenSTA1 11 and NB-STA 13 is 120 dB.

Redoing the calculations similar to the example of FIG. 2, ED_DL=−65 dBmis obtained. Furthermore, the UL signal from STA1 11 will be received at−85 dBm. The thermal noise in the AP 15 remains as above, i.e., −94 dBmin a 20 MHz channel, so that the SNR for a 20 MHz wide UL transmissionbecomes −85 dBm −(−94 dBm)=9 dB. Again, requiring that the NB-Wi-Fisignal should be 3 dB below the noise floor, i.e., received at −97 dBm,it follows that the maximum transmit power for the NB-Wi-Fi STA 13becomes −97 dBm+80 dB=−17 dBm.

Consequently, the NB-STA 13 would use ED_DL=−65 dBm to determine whetherthe channel should be considered idle, and if found idle the NB-Wi-FiSTA 13 would be allowed to use a maximum TX power of −17 dBm.

In the embodiments above the transmissions to and from legacy STAs 11were assumed to be 20 MHz, whereas the NB-Wi-Fi transmission was assumedto be only 2 MHz. In case the legacy transmission is based on OFDMA,such as e.g. IEEE 802.11ax, a slightly modified approach is possible.This will be described in the following embodiment.

It is supposed that OFDMA is used, and by means of example IEEE 802.11axis considered. For example, the OFDMA communication may be used betweenthe AP 15 and the STA1 11 (legacy station or wideband STA) shown in FIG.2 or FIG. 3 described above. FIG. 4 shows an illustration of possibleresource units (RUs) for a 20 MHz channel in IEEE 802.11ax. In 802.11ax,up to 9 RUs can be supported in a 20 MHz channel as illustrated in FIG.4. For further details, it is hereby referred to IEEE P802.11 WirelessLANs, “Specification Framework for TGax”, doc.:IEEE 802.11-15/0132r8,Sep. 2015, which is hereby incorporated by reference in its entirety.

The AP 15 can improve the chances for a NB-Wi-Fi STA 13 to gain accessto the channel, and also allow for an increased TX power by not usingthe RU which is used by the NB-Wi-Fi STA 13 in the DL transmission andin addition not schedule any UL transmission on the corresponding RU.

Suppose, as an example, that that the NB-Wi-Fi STA 13 is using the RU atthe lowest frequency, i.e., the left most RU with 26 sub-carriers inFIG. 4. Furthermore, again a deployment as the one described in FIG. 2is assumed. Since now there is no transmitted signal in thecorresponding 2 MHz, the detected energy will be considerably less incase of a DL transmission. The energy will not be identically zero asthere is some leakage in the IFFT used to generate the signal for theadjacent RU, but it will be, e.g., 30 dB smaller than if the RU would beallocated for user data transmission. The ED_DL is kept the same, i.e.−85 dBm. This means that the NB-Wi-Fi STA 13 will find the channel beingidle as the received power within a RU not used for data is very smallas described above. So by using OFDMA, and intentionally not allocatingdata for a specific RU, NB-Wi-Fi STAs using this RU will basicallyobtain a clear channel to access.

Further, there may also be a constraint on the allowed transmit powerthat can be used by the NB-Wi-Fi STA 13. In the first embodiment, thisconstraint was based on that it should not degrade a widebandtransmission in the UL, but the fact that the NB-Wi-Fi signal would notbe received by the AP was simply accepted. In case of OFDMA, the AP canalso explore this when scheduling the UL by not allocating any otherdata to the corresponding RU. In the deployment described in FIG. 2, itwas declared in the earlier embodiment that the TX power should bereduced to 3 dB so that the received power in a 2 MHz channel became -97dBm. However, since the received power from STA1 11 in the same 2 MHzchannel was −75 dBm, the SIR viewed from the NB-Wi-Fi STA 13 point ofview becomes −22 dB, which will make reception of the NB-Wi-Fi signalimpossible. Therefore, according to the present embodiment OFDMA is usedand the corresponding RU is not allocated for the UL. Now, since thepower from the wideband system within this RU now only is caused by someleakage from adjacent RUs, the SIR can be expected to be around 30 dBbetter than if the RU would be allocated for UL data transmission. Thus,a SIR of around 8 dB would be obtained, and also the NB-Wi-Fi signalwould be easily decodable by the AP 15.

Just as for the first embodiment, the ED_DL as well as the allowed TXpower are parameters that are derived for the individual STAs. It is, ofcourse, possible to look at the requirements for all involved STAs, andthen decide to use the most restrictive requirements for all STAs incase it would be seen as too complicated to keep track of a large set ofrequirements.

Any of the embodiments described below may be carried out in the contextof one or more of the technologies and embodiments described above. Inparticular, the embodiments described below may be implemented in a WLANcommunication network.

FIG. 5 shows a flowchart of a method for performing communication in awireless communication network. The method may be implemented by any ofthe network nodes described in this disclosure. In particular, themethod shown in FIG. 5 may be performed by the AP 15 shown in FIG. 2 or3.

As shown in FIG. 5, the method comprises the following steps:

Receiving 50 a signal transmitted by a user device in the wirelesscommunication network.

Measuring 52 a received power level at which the signal is received bythe network node.

Determining 54, based on a predefined transmit power level of thenetwork node, based on a predefined transmit power level of the userdevice and based on the received power level, a threshold power levelfor a clear channel assessment to be performed by the user device.

Triggering 56 transmitting an indication of the threshold power level tothe user device.

FIG. 6 shows a schematic block diagram of a network node 60 configuredto perform the method described above with reference to FIG. 5. Thenetwork node 60 may be an AP described in the present disclosure. Forexample, the network node 60 may correspond to the AP 15 described withregard to FIG. 2 or 3.

As shown in FIG. 6, the network node 60 comprises:

A receiving unit 61 configured to receive a signal transmitted by a userdevice in the wireless communication network.

A measuring unit 62 configured to measure a received power level atwhich the signal is received by the network node.

A determining unit 63 configured to determine, based on a predefinedtransmit power level of the network node, based on a predefined transmitpower level of the user device and based on the received power level, athreshold power level for a clear channel assessment to be performed bythe user device.

A triggering unit 64 configured to trigger transmitting an indication ofthe threshold power level to the user device.

The details described above with regard to the embodiments discussedwith reference to FIGS. 1 and 2 may also be applied with regard to themethod of FIG. 5 and with regard to the network node 60 of FIG. 6.

FIG. 7 shows a flowchart of a method for performing communication in awireless communication network. The method may be implemented by any ofthe stations (STAs) described in this disclosure and, in particular, byany of the NB-STAs described in this disclosure. In particular, themethod shown in FIG. 7 may be performed by the NB-STA 13 shown in FIG. 2or 3.

As shown in FIG. 7, the method comprises the following steps:

Receiving 70, from a network node of the wireless communication network,a threshold power level for a clear channel assessment to be performedby the user device in the wireless communication network;

Receiving 72, from the network node, a maximum transmit power level forsignals transmitted by the user device;

Triggering 74 performing the clear channel assessment in a channel ofthe wireless communication network; and

In case the channel is determined to be idle, transmitting 76 data tothe network node in the wireless communication network at a transmitpower level equal to or lower than the maximum transmit power level.

FIG. 8 shows a schematic block diagram of a user device 80 configured toperform the method described above with reference to FIG. 7. The userdevice 80 may be a NB-STA described in the present disclosure. Forexample, the user device 80 may correspond to the NB-STA 13 describedwith regard to FIG. 2 or 3.

As shown in FIG. 8, the user device 80 comprises:

A first receiving unit 82 configured to receive, from a network node ofthe wireless communication network, a threshold power level for a clearchannel assessment to be performed by the user device in the wirelesscommunication network.

A second receiving unit 84 configured to receive, from the network node,a maximum transmit power level for signals transmitted by the userdevice.

A triggering unit 86 configured to trigger performing the clear channelassessment in a channel of the wireless communication network.

A transmitting unit 88 configured to, in case the channel is determinedto be idle, transmit data to the network node in the wirelesscommunication network at a transmit power level equal to or lower thanthe maximum transmit power level

FIG. 9 shows a device 90 for performing communication in a wirelesscommunication network, according to the present disclosure. The device90 may be configured to carry out any of the methods described herein.For example, the device 90 may be configured to perform the method shownin FIG. 5 or FIG. 7. The device 90 may be or may comprise a network nodeaccording to the present disclosure or a user device according to thepresent disclosure.

The device 90 comprises a network interface 92 that is adapted tocommunicatively couple the device 90 to the wireless communicationnetwork (e.g., the WLAN). The device 90 further comprises a processor 94and a memory 96 containing instructions executable by the processor 94to cause the device 90 to carry out any of the methods described in thisdisclosure. In particular, the memory 96 may contain instructionsexecutable by the processor 94 to cause the device 90 to carry out anyof the methods according to FIG. 5 and FIG. 7.

As has become apparent from the above description, the techniqueaccording to the present disclosure, according to some embodiments,provides a means for devices not capable of using preamble detect (PD)to employ energy detect (ED) in a way ensuring that the devices will notharm legacy operation—something that otherwise is almost unavoidable.Narrowband devices cannot perform PD as the legacy preamble is awideband signal. In adjusting the narrowband devices' ED threshold theyare enabled to coexist with wideband systems. Thus the presentdisclosure allows for a narrowband Wi-Fi station (NB-Wi-Fi STA) toperform ED in order to send a packet to an access point (AP) withoutfirst being scheduled by the AP.

Many advantages of the present disclosure will be fully understood fromthe foregoing description, and it will be apparent that various changesmay be made in the form, construction and arrangement of the units anddevices without departing from the scope of the present disclosureand/or without sacrificing all of its advantages. Since the embodimentscan be varied in many ways, it will be recognized that the presentdisclosure should be limited only by the scope of the followingembodiments.

1-40. (canceled)
 41. A network node for performing communication in awireless communication network, the network node comprising: a receivingunit configured to receive a signal transmitted by a user device in thewireless communication network; a measuring unit configured to measure areceived power level at which the signal is received by the networknode; a determining unit configured to determine, based on a predefinedtransmit power level of the network node, based on a predefined transmitpower level of the user device, and based on the received power level, athreshold power level for a clear channel assessment to be performed bythe user device; and a triggering unit configured to triggertransmitting an indication of the threshold power level to the userdevice.
 42. A network node for performing communication in a wirelesscommunication network, the network node comprising: a network interfacethat is configured to communicatively couple the network node to thewireless communication network; a processor; and a memory containinginstructions executable by the processor to cause the network node to:receive a signal transmitted by a user device in the wirelesscommunication network; measure a received power level at which thesignal is received by the network node; determine, based on a predefinedtransmit power level of the network node, based on a predefined transmitpower level of the user device, and based on the received power level, athreshold power level for a clear channel assessment to be performed bythe user device; and trigger transmitting an indication of the thresholdpower level to the user device.
 43. A network node for performingcommunication in a wireless communication network, the network nodecomprising: a receiver configured to receive a signal transmitted by auser device in the wireless communication network; and one or moreprocessing circuits configured to: measure a received power level atwhich the signal is received by the network node; determine, based on apredefined transmit power level of the network node, based on apredefined transmit power level of the user device, and based on thereceived power level, a threshold power level for a clear channelassessment to be performed by the user device; and trigger transmittingan indication of the threshold power level to the user device.
 44. Thenetwork node of claim 43, wherein the one or more processing circuitsare further configured to: determine, based on the received power leveland based on the predefined transmit power level of the user device, apath loss of the signal transmitted from the user device to the networknode, wherein the network node is configured to determine the thresholdpower level based on the predefined transmit power level of the networknode and based on the path loss.
 45. The network node of claim 44,wherein the one or more processing circuits are further configured to:set a desired maximum received power level for signals to be received bythe network node from the user device; determine, based on the maximumreceived power level and based on the path loss, a maximum transmitpower level for signals transmitted by the user device; triggertransmitting an indication of the maximum transmit power level to theuser device.
 46. The network node of claim 45, wherein the one or moreprocessing circuits are configured to set the desired maximum receivedpower level for signals to be received by the network node from the userdevice so as to correspond to a predefined proportion of a thermal noisepower level of signals received by the network node.
 47. The networknode of claim 43, wherein the one or more processing circuits arefurther configured to receive, via the receiver of the network node,data transmitted from the user device.
 48. The network node of claim 43,wherein the one or more processing circuits are further configured totransmit signals using an orthogonal frequency-division multiple access(OFDMA) modulation scheme in which one or more resource units (RUs) areassigned for transmissions to and/or from a particular user device, theone or more processing circuits being further configured to: receive,via the receiver of the network node, a signal transmitted by the userdevice; determine, based on the received signal, one or more RUs of theOFDMA modulation scheme used by the network node, in which the receivedsignal is transmitted by the user device; exclude the one or more RUsfrom a list of RUs available for transmissions from the network node toa further user device; and trigger transmitting data to the further userdevice by using one or more RUs of the list of RUs.
 49. The network nodeof claim 43, wherein the one or more processing circuits are furtherconfigured to transmit signals, via a transmitter of the network node,using an orthogonal frequency-division multiple access (OFDMA)modulation scheme in which one or more resource units (RUs) are assignedfor transmissions to and/or from a particular user device, the one ormore processing circuits being configured to: receive, via the receiverof the network node, a signal transmitted by the user device; determine,based on the received signal, one or more RUs of the OFDMA modulationscheme used by the network node, in which the received signal istransmitted by the user device; exclude the one or more RUs from a listof RUs available for transmissions from a further user device to thenetwork node; and trigger scheduling a transmission from the furtheruser device to the network node by using one or more RUs of the list ofRUs.
 50. The network node of claim 49, wherein the one or moreprocessing circuits are configured to trigger the scheduling of thetransmission from the further user device to the network node bytransmitting a scheduling message to the further user device, whereinthe scheduling message comprises an indication of the one or more RUs ofthe list of RUs to be used by the further user device for thetransmission from the further user device to the network node.
 51. Thenetwork node of claim 43, wherein the wireless communication network isa wireless local area network (WLAN) operating in the IEEE 802.11standard family and wherein the network node comprises an access pointof the WLAN.
 52. The network node of claim 43, wherein the wirelesscommunication network is a wireless local area network (WLAN)) operatingin the IEEE 802.11 standard family and wherein the user device comprisesa station (STA) of the WLAN.
 53. The network node of claim 43, whereinthe network node is configured to communicate with a first type of userdevice and a second type of user device, wherein the second type of userdevice supports wider bandwidths than the first type of user device. 54.The network node of claim 53, wherein the first type of user device onlysupports communication within a bandwidth of 2 MHz or less.
 55. Thenetwork node of claim 53, wherein the second type of user devicesupports communication within a bandwidth of 10 MHz or more.
 56. A userdevice for performing communication in a wireless communication network,the user device comprising: a first receiving unit configured toreceive, from a network node of the wireless communication network, athreshold power level for a clear channel assessment to be performed bythe user device in the wireless communication network; a secondreceiving unit configured to receive, from the network node, a maximumtransmit power level for signals transmitted by the user device; atriggering unit configured to trigger performing the clear channelassessment in a channel of the wireless communication network; and atransmitting unit configured to, in case the channel is determined to beidle, transmit data to the network node in the wireless communicationnetwork at a transmit power level equal to or lower than the maximumtransmit power level.
 57. A user device for performing communication ina wireless communication network, the user device comprising: a networkinterface that is adapted to communicatively couple the user device tothe wireless communication network; a processor; and a memory containinginstructions executable by the processor to cause the user device to:receive, from a network node of the wireless communication network, athreshold power level for a clear channel assessment to be performed bythe user device in the wireless communication network; receive, from thenetwork node, a maximum transmit power level for signals transmitted bythe user device; trigger performing the clear channel assessment in achannel of the wireless communication network; and in case the channelis determined to be idle, transmit data to the network node in thewireless communication network at a transmit power level equal to orlower than the maximum transmit power level.
 58. A user device forperforming communication in a wireless communication network, the userdevice being configured to: receive, from a network node of the wirelesscommunication network, a threshold power level for a clear channelassessment to be performed by the user device in the wirelesscommunication network; receive, from the network node, a maximumtransmit power level for signals transmitted by the user device; triggerperforming the clear channel assessment in a channel of the wirelesscommunication network; and in case the channel is determined to be idle,transmit data to the network node in the wireless communication networkat a transmit power level equal to or lower than the maximum transmitpower level.
 59. The user device of claim 58, wherein the wirelesscommunication network is a wireless local area network (WLAN) operatingin the IEEE 802.11 standard family and wherein the network nodecomprises an access point of the WLAN.
 60. The user device of claim 58,wherein the wireless communication network is a wireless local areanetwork (WLAN) operating in the IEEE 802.11 standard family and whereinthe user device comprises a station (STA) of the WLAN.
 61. The userdevice of claim 58, wherein the user device is a first type of userdevice only supporting communication within a bandwidth of 2 MHz orless.
 62. A method for performing communication in a wirelesscommunication network, the method being performed by a network node andthe method comprising: receiving a signal transmitted by a user devicein the wireless communication network; measuring a received power levelat which the signal is received by the network node; determining, basedon a predefined transmit power level of the network node, based on apredefined transmit power level of the user device, and based on thereceived power level, a threshold power level for a clear channelassessment to be performed by the user device; and triggeringtransmitting an indication of the threshold power level to the userdevice.
 63. The method of claim 62, further comprising: determining,based on the received power level and based on the predefined transmitpower level of the user device, a path loss of the signal transmittedfrom the user device to the network node, wherein the threshold powerlevel is determined based on the predefined transmit power level of thenetwork node and based on the path loss.
 64. The method of claim 63,further comprising: setting a desired maximum received power level forsignals to be received by the network node from the user device;determining, based on the maximum received power level and based on thepath loss, a maximum transmit power level for signals transmitted by theuser device; triggering transmitting an indication of the maximumtransmit power level to the user device.
 65. The method of claim 64,wherein the step of setting the desired maximum received power level forsignals to be received by the network node from the user devicecomprises setting the maximum received power level so as to correspondto a predefined proportion of a thermal noise power level of signalsreceived by the network node.
 66. The method of claim 62, furthercomprising: receiving data transmitted from the user device.
 67. Themethod of claim 62, further comprising: transmitting signals using anorthogonal frequency-division multiple access (OFDMA) modulation schemein which one or more resource units (RUs) are assigned for transmissionsto and/or from a particular user device; receiving a signal transmittedby the user device; determining, based on the received signal, one ormore RUs of the OFDMA modulation scheme used by the network node, inwhich the received signal is transmitted by the user device; excludingthe one or more RUs from a list of RUs available for transmissions fromthe network node to a further user device; and triggering transmittingdata to the further user device by using one or more RUs of the list ofRUs.
 68. The method of claim 62, further comprising: transmittingsignals using an orthogonal frequency-division multiple access (OFDMA)modulation scheme in which one or more resource units (RUs) are assignedfor transmissions to and/or from a particular user device; receiving asignal transmitted by the user device; determining, based on thereceived signal, one or more RUs of the OFDMA modulation scheme used bythe network node, in which the received signal is transmitted by theuser device; excluding the one or more RUs from a list of RUs availablefor transmissions from a further user device to the network node; andtriggering scheduling a transmission from the further user device to thenetwork node by using one or more RUs of the list of RUs.
 69. The methodof claim 68, wherein the step of triggering scheduling the transmissionfrom the further user device to the network node comprises transmittinga scheduling message to the further user device, wherein the schedulingmessage comprises an indication of the one or more RUs of the list ofRUs to be used by the further user device for the transmission from thefurther user device to the network node.
 70. The method of claim 62,wherein the wireless communication network is a wireless local areanetwork, WLAN, operating in the IEEE 802.11 standard family and whereinthe network node comprises an access point of the WLAN.
 71. The methodof claim 62, wherein the wireless communication network is a wirelesslocal area network, WLAN, operating in the IEEE 802.11 standard familyand wherein the user device comprises a station, STA, of the WLAN. 72.The method of claim 62, further comprising: communicating with a firsttype of user device and a second type of user device, wherein the secondtype of user device supports wider bandwidths than the first type ofuser device.
 73. The method of claim 72, wherein the first type of userdevice only supports communication within a bandwidth of 2 MHz or less.74. The method of claim 72, wherein the second type of user devicesupports communication within a bandwidth of 10 MHz or more.
 75. Amethod for performing communication in a wireless communication network,the method being performed by a user device and the method comprising:receiving, from a network node of the wireless communication network, athreshold power level for a clear channel assessment to be performed bythe user device in the wireless communication network; receiving, fromthe network node, a maximum transmit power level for signals transmittedby the user device; triggering performing the clear channel assessmentin a channel of the wireless communication network; and in case thechannel is determined to be idle, transmitting data to the network nodein the wireless communication network at a transmit power level equal toor lower than the maximum transmit power level.
 76. The method of claim75, wherein the wireless communication network is a wireless local areanetwork (WLAN) operating in the IEEE 802.11 standard family and whereinthe network node comprises an access point of the WLAN.
 77. The methodof claim 75, wherein the wireless communication network is a wirelesslocal area network (WLAN) operating in the IEEE 802.11 standard familyand wherein the user device comprises a station (STA) of the WLAN. 78.The method of claim 75, wherein the user device is a first type of userdevice only supporting communication within a bandwidth of 2 MHz orless.